The present invention generally relates to methods for coating or printing plastic foils or films.
The invention is particularly directed to the coating or printing of a plastic film with hydrous or, respectively, aqueous coating agents, solvent-containing coating agents such as ethanol, methanol, isopropanol, xylol, 1-butanone, methyl ethyl ketone, dimethylformamide, methyl glycol acetate and tetrahydrofuran or mixtures of aqueous coating agents and solvent-containing coating agents, UV-curable lacquers or inks as well as PVC pastes. The invention is particularly directed to a coating of a plastic film with a hydrous coating agent, particularly printing with a water-soluble ink.
The invention is also directed to the coating and printing of the plastic film by way of transfer printing comprising the work steps of coating the conveyed ribbon with hydrous coating agents, solvent-containing coating agents or mixtures thereof, UV-curable lacquers or inks, of drying the applied agent or the applied ink, of depositing the film onto the coated or printed tape, laminating the film upon application of heat (160.degree.-200.degree. C.) and pressure and thereafter cooling and separating the plastic film from the conveyor belt.
The invention, finally, is directed to a method for coating a substrate such as tricot, fabric, fleece or felt by way of transfer coating comprising the following work steps:
a) coating an endless conveyor belt with aqueous coating agents, solvent-containing coating agents or mixtures of aqueous and solvent-containing coating agents as well as PVC pastes; PA1 b) drying the applied agent; PA1 c) cooling the agent via cooling drums; PA1 d) re-coating with the aforementioned coating agents (see step a)); PA1 e) potentially laminating a substrate such as tricot, fabric, fleece or felt into the as yet wet material; PA1 f) drying and jelling upon application of heat up to 200.degree. C.; PA1 g) cooling the laminate and removal thereof from the conveyor belt. PA1 a) coating the conveyor belt (in the cold condition) with the coating agents: aqueous coating agent, solvent-containing coating agent or mixtures thereof, UV-curable lacquers or inks; PA1 b) drying the applied agent or the applied ink with heat or UV; PA1 c) depositing the film on the as yet hot, coated or printed tape (given UV products, the tape must be heated); PA1 d) laminating the film under the influence of heat, i.e. temperatures of 160.degree.-250.degree. C., in particular 180.degree. C.; and PA1 e) cooling and separating the plastic film from the conveyor belt.
Great quantities of plastic films in the manufacture of data carrier tapes such as, for example, audio and video tapes are already coated with solvent-containing and, in particular, with hydrous coating agents that contain the critical particles for the data storage. The plastic films are thereby conducted over drum straighteners and dare only be heated to comparatively low temperatures due to the shrinkage. These low temperatures require extremely long drying paths, for example up to more than 160 m, for effective drying of the coating agent.
There is therefore a great need for a faster drying capability and for lowering manufacturing costs of the tape coating systems and, thus, of the data carrier tapes.
German published application 37 29 450 discloses a method for double-sided coating of a film tape, whereby two tapes are joined to one another at their edges, these then running through a coating tape as sandwich or laminate, whereupon a treatment of the coated layer ensues and, finally, the two tapes joined to one another only at their edges are in turn separated from one another in that the connecting edges are cut off, so that two tapes coated at one side are ultimately present as final product according to German published application 37 29 450.
German published application 36 05 426 discloses a method for surface-processing of polyethylene films. An ink is applied onto a printed film that is applied on a carrier of metal or paper. When transferring the printed film onto a polyethylene film, this is in turn pulled off from the carrier material.
German AS 11 82 560 discloses a method for manufacturing packaging materials of water-sensitive films by coating with aqueous dispersions, whereby two webs of the films pass a nip into which the dispersion is introduced, and the films are in turn separated when they depart the nip.
Solvent-containing inks are usually employed when printing plastic films, this involving ever greater problems in view of the elimination or, respectively, reclamation of the solvents occasioned by stricter and stricter environmental regulations.
There is therefore an increasing need here for printing plastic films with inks that are free of solvent, i.e. for example, with water-soluble ink or with hydrous agents, i.e. mixtures of aqueous coating agents and coating agents that contain solvent.
The employment of water-soluble inks called for in and of itself, however, has hitherto presented difficulties since the required color fastness leaves a great deal to be desired, namely regardless of the printing technique employed.